The Italian Situation
I have done a lot of background reading about the Italian Surrender.
Basically, there was little to no fighting betwene Italian and RSI forces. They actually went out of their way to avoid fighting eachother (Parsisan forces were another issue, they hated the RSI). There were actual accounts of Italian fighters purposely poorly escorting US bombers when RSI fighters were in the region for two reasons. #1. they did not want to shoot down fellow Italian pilots, and #2. did not like the idea that these American bombers were bombing Italian cities on these missions.
Basically what happened to the Italian Army is...
IN ITALY:
The entire nation was divided into two parts. An Allied half (in the South) and an Axis half (in the North). Basically all Italian troops were disarmed in these regions by Allied and Axis forces. A certain percentage volunteered to serve in the respective regions, while the remainder went into respective POW camps. A very high number of Italians in the South joined the Allied forces, but only around 10% of those in the north joined the RSI (which grew to a maximum force size of 150 000). Also, many troops may not have volunteered for service beyond following orders and/or geography. There were some instances of Italian defiance, but that was only toward foreign forces (primarily against the Germans, there was very little resistence to the Allies).
This is what primarily happened for the air force units. Since they were highly trained, they were 'forced' into action by their respective commands, irregardless of personal politics. So, if an air unit was located in the North (a German controlled region) chances were that they would be flying for the RSI. The Italian government did issue a request to all pilots to fly their aircraft to Allied zones, but only a few hundred were able to do so that were located in the north.
The only fighting that really took place was between Italian and German forces. There was some fighting around and to the South of Rome (the extent of German influence) where Germany managed to take back Rome, but the Italian forces stopped further advances.
Commanders had very little influence over what happened in the region. If a commander in the North was pro Allied, there was no thought about proclaiming it, but rather was (with their men) marched off to POW camps. The only real fighting ocurred between Italians and other nationals was really on the fringes, where hope existed (like in Central Italy, the Aagean Sea, and Greece).
IN THE BALKANS:
Many troops (inlcuiding entire divisions) joined Partisan units, while the vast majority ended up as German POW's.
IN THE AEGEAN:
Troops in Rhodes remained loyal (but were eventually disarmed by the Germans and put into POW camps), but those in the Northern Islands were directly definiant to Germany and officially joined the Allies (along with some Italian garrisons in Western Greece).
COMMANDERS:
The vast majority of military commanders sided with the Allied Italian Government, while only a few went with the RSI. Also, the Fascist Militia put up some of the strongest resistence to the Germans in Italy. They had very little choice when it came to resisting or not. If they chose to resist, they tended to disband their forces and joined Partisan organizations, or decided that the situation was hopeless and surrendered their forces.
SUMMARY:
Italian soldiers did not have much control over their allegiance after the Surrender. Virtually all of them went to POW camps, and then formed their respective Allied or Axis Italian formations. There was no civil war. It would be interesting to see what would happen with an Italian Civil War, but I don't think that the political situation would have resulted in one. The Italian Army was paralized with indecision. The Germans found it safer to disarm all Italian forces, while the Allies required all of the Italian units to surrender.
Hitler had given up on any form of an Independent Italy after the Surrender. The RSI was formed mainly as a way in keeping Northern Italy somewhat pacified, due to the perception that they were at least under some form of Italian rule. Also, the RSI was valueable in their rearguard operations (fighting partisans and CAP against Allied bombing). Otherwize, Northern Italy was effectively under German military control.
SOLUTION:
The current situation will almost always result in Italy being overrun by Germany. I am going to have the Italian Peace accord with the Allies require Italy to give up virtually all of their Southern Italian Provinces to the Allies (half British, half American if the US is in the war).
Also, I have seen allies come to the rescue of their, well, allies. HOWEVER, this only ocurrs IF territory adjacent to ENEMY territory is the territory of the Alliance leader.
I did some tests as Italy vs. Germany and the RSI. When I quickly overran the most southern German Italian provinces and ran up against RSI territories and took them, and controlled provinces directly adjacent to core German provinces, I was met by an Axis force comprising of German, Croatian, Bulgarian, Hungarian and Vichy French. HOWEVER, when they pushed me back, the conquered territory went to the RSI. When Allied Italian territory was no longer adjacent to Axis German territory, the massive coalition force started to disperse. When I retook that RSI province, they quickly came back to finish me off, and when I pulled back, they then dispersed again. The third time I allowed them to push me back to territory that was given to Germany during the Italian Peace event, and remained German when the Axis occupied it. The Axis attack force did not disperse, but kept on coming down the boot of Italy. This force remained an international one as well.
So, it appears that coalition forces will keep their integrity and actually defend/advance together IF the territory under question IS, or IS IN CONTACT WITH territory from the key player in the Alliance. I have yet to determine wether or not this works with the Allies (wether coalition forces fight better on British territory vs. French or American), but I assume it to be so.